The present invention claims priority on PCT Application Ser. No. PCT/US2007/079119 filed Sep. 21, 2007, which in turn claims priority on U.S. Provisional Application Ser. No. 60/846,154 filed Sep. 21, 2006. The various embodiments of the present invention relate generally to medical devices, and particularly to an implant for use within a body to repair various types of body passageways, and even more particularly to an expandable graph which is useful in repairing blood vessels narrowed or occluded by disease. The medical device at least partially includes novel refractoty metals that have specific design features that accommodate the intrinsic properties of the metal.
Medical treatment of various illnesses or diseases commonly includes the use of one or more medical devices. Two types of medical devices that are commonly used to repair various types of body passageways are an expandable graft or stent, or a surgical graft. These devices have been implanted in various areas of the mammalian anatomy. One purpose of a stent is to open a blocked or partially blocked body passageway. When a stent is used in a blood vessel, the stent is used to open the occluded vessel to achieve improved blood flow which is necessary to provide for the anatomical function of an organ. The procedure of opening a blocked or partially blocked body passageway commonly includes the use of one or more stents in combination with other medical devices such as, but not limited to, an introducer sheath, a guiding catheter, a guide wire, an angioplasty balloon, etc.
Various physical attributes of a stent can contribute directly to the success rate of the device. These physical attributes include radiopacity, hoop strength, radial force, thickness of the metal, dimensions of the metal and the like. Cobalt and chromium and stainless steel are commonly used to form stents and have physical characteristics that are common throughout the design and functional phase. These materials are commonly used since such materials having a known history of safety, effectiveness, ease of manufacturing and biocompatibility.
The materials commonly used to form prior stents are biostable materials that remain in the blood vessel long after the stent has achieved its function. As such, the continued presence of the stent in the blood vessel can increase the risks associated with thrombosis, in-stent restenosis, vascular narrowing and/or restenosis in the blood vessel at the location of the stent. The presence of the stent in the blood vessel also can create a potential obstruction to later medical procedures that attempt to correct problems in a body passageway upstream from the stent. The stent can also be prone to fracturing overtime, especially when the stent is located in regions exposed to bending (e.g., leg, aims, neck, etc.). The repeated bending of the stent can eventually fatigue the stent, thereby resulting in one or more portions of the stent fracturing and/or becoming loose from the stent. These fractures (e.g., strut fractures, etc.) and/or loose portions of the stent can result in damage to the blood vessel and/or one or more regions of the vascular system down stream of the stent. The over all strut thickness also has the ability to hinder blood flow and thus remains a hindrance to healing within the mammalian anatomy.